The present invention relates to a milling cutter and a cutting insert for machining metal workpieces in general and the cams of camshafts in particular.
A milling cutter of this type is disclosed in JP 2000052131. The milling cutter disclosed in this publication comprises groups of two tangentially oriented cutting inserts arranged in pairs a circumferentially staggered formation. The two inserts of a given pair overlap at least partially when superimposed. As shown in FIG. 8 of this publication the milling cutter is only suitable for machining the flank (outer peripheral curved surface) of the cams of a camshaft.
Another milling cutter for machining the cams of camshafts is disclosed in JP 11138325. This milling cutter not only machines the flank of a cam but also chamfers the edges of the flank. The milling cutter disclosed in this publication also comprises groups of cutting inserts arranged in a circumferentially staggered formation. There are first pairs of cutting inserts that at least partially overlap when superimposed that machine the flank of the cam, as in JP 2000052131. In addition, there are second pairs of cutting inserts, different from the first pairs, located on the rim on the cutter in a circumferentially staggered manner, that chamfer the edges of the flank.
It is an object of the present invention to provide a milling cutter and a cutting insert capable of machining the flank of a cam of a camshaft and also of chamfering the edges of the flank, wherein the milling cutter comprises groups of two radially oriented identical cutting inserts arranged in a circumferentially staggered formation and each cutting insert has eight cutting edges.
In accordance with the present invention there is provided an indexable cutting insert for use in a milling cutter comprising:
generally square shaped top and bottom surfaces;
four substantially identical side surfaces extending between the top surface and the bottom surface;
two diametrically opposite protuberances extending away from each other in a top or bottom view of the cutting insert, each protuberance having a peripheral side surface comprising an intermediate side surface and two minor side surfaces, the intermediate side surface being located between and merging with the two minor side surfaces, each side surface comprising a major side surface connected to an adjacent minor side surface, adjacent major side surfaces merging at two diametrically opposite corner edges of the cutting insert;
eight identical major cutting edges, comprising four major cutting edges formed at the intersection of the major side surfaces with the top surface and four major cutting edges formed at the intersection of the major side surfaces with the bottom surface; and
eight identical minor cutting edges, comprising four minor cutting edges formed at the intersection of the minor side surfaces with the top surface and four minor cutting edges formed at the intersection of the minor side surfaces with the bottom surface, each minor cutting edge being connected to an adjacent major cutting edge.
In accordance with a preferred embodiment of the present invention, the minor cutting edges are shorter than the major cutting edges and form therewith an obtuse angle in a top or bottom view of the cutting insert.
Further in accordance with a preferred embodiment of the present invention, each side surface has a varying height dimension.
Preferably, the height dimension has a minimum value in a central region of the side surface.
Further preferably, the height dimension decreases monotonically from a maximum value at an outer region of the side surface to the minimum value at the central region.
Typically, the top and bottom surfaces are provided with a chip groove adjacent and extending longitudinally along the major and minor cutting edges.
Preferably, the top surface is provided with a top abutment surface generally centrally located with respect to the major cutting edges and the bottom surface is provided with a bottom abutment surface generally centrally located with respect to the major cutting edges and generally facing away from the top abutment surface.
In accordance with a preferred embodiment, the top and bottom abutment surfaces are flat and parallel to each other and separated by a given distance.
Further in accordance with a preferred embodiment, the given distance between the top and bottom abutment surfaces is at least equal to the maximum value of the height dimension of the side surfaces.
If desired, the cutting insert is provided with a land extending from the major and minor cutting edges towards the chip groove.
There is also provided in accordance with the present invention, a milling cutter comprising a tool body having the general form of a circular disk and a plurality of identical cutting inserts releasably mounted in insert pockets;
the tool body having two oppositely facing generally circular side faces connected by a peripheral mounting face, an axis of rotation passing through the side faces, the axis of rotation defining a direction of rotation of the milling cutter;
the insert pockets being spaced angularly around the peripheral mounting face;
the cutting inserts comprising:
generally square shaped top and bottom surfaces;
four substantially identical side surfaces extending between the bottom surface and the top surface;
two diametrically opposite protuberances extending away from each other in a top or bottom view of the cutting insert, each protuberance having a peripheral side surface comprising and intermediate side surface and two minor side surfaces, the intermediate side surface being located between and merging with the two minor side surfaces, each side surface comprising a major side surface connected to an adjacent minor side surface, adjacent major side surfaces merging at two diametrically opposite corner edges of the cutting insert;
eight identical major cutting edges, formed at the intersection of the major side surfaces with the top and bottom surfaces; and
eight identical minor cutting edges, formed at the intersection of the minor side surfaces with the top and bottom surfaces, each minor cutting edge being connected to an adjacent major cutting edge;
the cutting inserts being arranged in a staggered formation in pairs with one of the top or bottom abutment surfaces of each cutting insert facing in the direction of rotation,
a first cutting insert of a given pair of cutting inserts having a radially and axially outermost first protuberance protruding axially at least partially from a first side face of the tool body, a second cutting insert of the given pair of cutting inserts having a radially and axially outermost second protuberance protruding axially at least partially from a second side face of the tool body.
In accordance with a preferred embodiment, the first cutting insert has a first major cutting edge located at a given radial distance from the axis of rotation and the second cutting insert has a second major operative cutting edge located at the same given radial distance.
Generally, the first and second protuberances protrude radially at least partially from the peripheral mounting face.